The present invention relates to a closed-loop multistage cleaning system and process, particularly one adapted to clean printed circuit boards of flux residue after a soldering operation.
Various systems and processes exist for cleaning printed circuit boards of flux residue. In general, such systems are characterized by a conveyer that transports the printed circuit boards to be cleaned through a housing in which they are subjected to a washing operation, then a rinsing operation, then a drying operation. Such systems in the past have been designed to accept water from a supply, such as a municipal water supply, use it in the washing and rising operation, then dispose of the water to an appropriate drain. More recently, some systems have been designed to recycle at least some of the water in the system through a processor that removes from the water residue entrained during the cleaning operation, then to return the processed water to the cleaning system, the processed water being of a purity at least comparable to that coming from a municipal water supply.
Aqueous cleaning systems such as the foregoing, whether combined with a closed-loop recycling and purification system or not, are designed to use a minimum amount of water. This limitation places significant constraints on the design of the cleaning system. Without such constraints an improved cleaning system could be designed.
Accordingly, one object of the present invention is to design an improved aqueous cleaning system and process for printed circuit boards and the like. Another object is to provide such a system that is compact, energy efficient, and that discharges to the drain a minimum of amount water. These and other objects of the present invention will be apparent to those skilled in the field from the following description of preferred embodiments.